My windshield wipers work perfectly when I have them on low/intermittent, but when I bump them up to high, they struggle to get across the windshield. At first I thought it might be the motor, but given that they work fine on low, I'm thinking it could be the switch..?

Any insight would be super helpful. I'm very much a beginner when it comes to all things cars, but would love to be able to diagnose and fix this myself, if possible, to save some cash!